Electronic image sensors are widely used to produce video and photographic images. The electronic image sensors typically comprise pixel sensors that are arranged in an array of rows and columns. The photosensitive volume of conventional CMOS image sensor pixels is limited to a photodiode area such that the pixel photosensitivity is limited by either the photodiode region or the associated photo conversion gain. The pixel sensitivity reaches a saturation level as the photodiode area keeps increasing. Accordingly, there is a need to improve the sensitivity of conventional pixels.
An appreciation of the present invention and its improvements can be obtained by reference to the accompanying drawings, which are briefly summarized below, to the following detailed description of illustrated embodiments of the invention, and to the appended claims.